1. Field of the Invention
The invention is related to computing systems and more particularly to dynamic voltage control of computing systems.
2. Description of the Related Art
A typical microprocessor may include multiple power planes, some of which receive fixed voltage levels and others which receive dynamically varied voltage levels. A voltage regulator coupled to the microprocessor provides the dynamically varied voltage to the power planes. The dynamically varied voltage levels may be altered according to various states (e.g., Advanced Configuration and Power Interface power-saving states and hardware thermal control states). The microprocessor communicates a target voltage level to the voltage regulator using a parallel interface or a serial interface, e.g., a parallel voltage level identifier (PVI) interface or a serial voltage level identifier (SVI) interface.
A typical voltage regulator provides voltage levels with multiple bits of precision (e.g., 12-bit precision). The microprocessor sends n voltage identifier codes (where n is the number of power planes supported by the microprocessor) to the voltage regulator. When using a serial interface (e.g., SVI), the microprocessor sends those n voltage identifier codes using a fixed number of pins (e.g., two pins). However, communication of a target voltage level for one or more power planes over the serial interface can be time consuming and impacts the latency of the microprocessor when switching from one performance state to another. When using a parallel approach, the microprocessor requires a number of pins based on n and the number of bits communicated.